Thin film magnetic head and manufacturing method of the same

ABSTRACT

A thin film magnetic head which is one of a plurality of thin film magnetic heads produced from a single substrate. This magnetic head includes a slider with at least one end face, at least one electromagnetic transducer element formed on the end face of the slider, a plurality of input and output terminals formed on the end face of the slider and electrically connected to the transducer element, a protection layer formed on the end face to cover at least the transducer element, and an identification mark for identifying the magnetic head, described on the protection layer on the end face of the slider.

FIELD OF THE INVENTION

The present invention relates to a thin film magnetic head fabricated bysimultaneously forming a plurality of head elements on a singlesubstrate and then by cutting the substrate to separate the formedrespective head elements, and also relates to a method of manufacturingthe same.

DESCRIPTION OF THE RELATED ART

Thin film magnetic heads are in general fabricated by using aphotolithography technology, a thin film forming technology, an etchingtechnology and a grinding and polishing technology. On a substrate(wafer), a matrix of magnetic head elements (electromagnetic transducerelements) and their input and output terminals are simultaneouslyformed. Then, the substrate is cut into a plurality of rectangularsliced blocks (bars) so that each of the bars includes a plurality ofmagnetic head elements and of input and output terminals aligned in asingle-row. Thereafter, one surface of each of the bars is subjected togrinding and polishing processes to shape rails and air bearing surfacesof the sliders, and then, by cutting the bar, individual magnetic headsare finally obtained.

Each lot of fabricating thin film magnetic heads is in generaldetermined to a unit corresponding to a single substrate (wafer) or aplurality of substrates (wafers). Since the above-mentioned processesare repeated at every lot, there may be some differences in sizes and/orin characteristics between the manufactured heads from the samesubstrate, between the manufactured heads from the different substratesin the same lot, or between the manufactured heads from the differentlots. Also, some defective heads may be included in the manufacturedmagnetic heads from the same substrate, in the manufactured heads fromthe different substrates in the same lot, or in the manufactured headsfrom the different lots.

Accordingly, in order to manage and to control the manufacturingprocesses so as to prevent defective heads from increasing, it isnecessary to provide for each magnetic head an identification number orsymbol which indicates a location of the head in a substrate, a locationof the substrate in a lot, and/or a lot number. The identificationnumbers or symbols of the respective magnetic heads will be required formanaging the heads at a cutting process in which the bar will beseparated into individual magnetic heads and for adequately eliminatingthe defective heads.

Japanese Patent Unexamined Publication No. 62(1987)-20116 discloses aconventional art for providing such identification numbers or symbols toa thin film magnetic head. In this known art, the magnetic head has anidentification number written, using a photolithography technology,within an unoccupied area on an element-formed face of the head as shownin FIG. 1. This identification number was written, before cutting thesubstrate into bars, on its front surface. The magnetic head also has anidentification number written, by a laser beam machining, on an oppositeface of the element-formed face (air-flow intake side face of theslider) as shown in FIG. 2. This identification number was written,before cutting the substrate into bars, on its rear surface.

In these FIGS. 1 and 2, reference numeral 10 denotes a slider of thethin film magnetic head, 11 and 12 denote electromagnetic transducerelements and input and output terminals which are formed on an air-flowoutlet side face 10a of the slider 10, respectively. In the first layerof this end face 10a, an identification number 13 is written byphotolithography, and also an identification number 14 is written, by alaser beam machining, on an air-flow intake side face 10b of the slider10. These identification numbers 13 and 14 are the same number whichindicates a location of the magnetic head in a substrate.

Japanese Patent Unexamined Publication No. 4(1992)-102214 discloses ananother conventional art for providing an identification number orsymbol to a thin film magnetic head. In this latter known art, anidentification number is written, using a photolithography technology ora laser beam machining technology, on an air-flow intake side face ofthe slider. This identification number was written, before cutting thesubstrate into bars, on its rear surface. The identification number inthis case is information for indicating a location of the magnetic headin the substrate, identifying the substrate itself and indicatingspecification of the head.

The above-mentioned conventional arts however have following problems.

(1) According to the conventional art for forming an identificationnumber or symbol in a first layer on an air-flow outlet side face of theslider (on a front surface of the substrate) by photolithography, sincethe identification number or symbol has to be written within an areaunoccupied by electromagnetic transducer elements and input and outputterminals which are formed on this same face, a large amount ofidentification number cannot be written. Particularly, since recent thinfilm magnetic heads for high recording density have been greatlydownsized, an unoccupied area on an element-formed face of each of theheads becomes extremely small causing the amount of identificationnumber which can be written thereon to extremely reduce.

(2) The another conventional art for forming an identification number orsymbol on a rear surface of the substrate cannot be used in a certainmethod for manufacturing a thin film magnetic head, in which a portionof the substrate near the rear surface is sliced and removed after theidentification number or symbol is formed. For example, in amanufacturing method proposed in U.S. patent application Ser. No.08/595,923 according to the same assignee as that of this application, asubstrate with a thickness more than a desired slider length is used forforming the electromagnetic transducer elements and after that a portionof the substrate near the rear surface is sliced and removed so that alength of the substrate becomes equal to the desired slider length. Thismethod can prevent a possible bend toward the substrate thickness tooccur resulting no defective sliders in dimension due to this directionbend in spite of downsizing of the slider. In such case, of course, theidentification number or symbol formed on the rear surface of thesubstrate will be lost at the slicing and removing process.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a thinfilm magnetic head and a method of manufacturing the head, wherebyenough amount of identification information of the head can be formed inspite of downsizing.

Another object of the present invention is to provide a thin filmmagnetic head and a method of manufacturing the head, wherebyidentification information of the head can be held even if a portion ofthe substrate near its rear surface is sliced and removed during themanufacturing processes.

Further object of the present invention is to provide a thin filmmagnetic head and a method of manufacturing the head, wherebyidentification information of the head can be formed without greatlymodifying the conventional manufacturing processes.

The present invention relates to a thin film magnetic head which is oneof a plurality of thin film magnetic heads produced from a singlesubstrate. This magnetic head includes a slider with at least one endface, at least one electromagnetic transducer element formed on the endface of the slider, a plurality of input and output terminals formed onthe end face of the slider and electrically connected to the transducerelement a protection layer formed on the end face to cover at least thetransducer element, and an identification mark for identifying themagnetic head, described on the protection layer on the end face of theslider.

Since the identification mark is formed on the protection layer, thisidentification mark can be made in any region on the end face so long aspresence of the protection layer. Namely, the identification mark can bemade even on the transducer element and lead conductors which connectthe transducer with the input and output terminals. Thus, enough amountof identification information can be described on the end face even ifthe thin film magnetic head is greatly downsized.

Also, according to the present invention, to form the identificationmark on the protection layer will result no modification of processconditions in a protection layer forming process which may be one of themost difficult manufacturing processes of the thin film magnetic head.Therefore, the formation process of the identification mark can be veryeasily introduced into the manufacturing processes of the magnetic head.

Furthermore, since the identification mark is formed on theelement-forming face of the slider, the identification marks can be heldeven if a portion of the substrate near its rear surface is sliced andremoved due to downsizing.

It is preferred that the identification mark represents an identifyinginformation which can differ for each substrate, such as at least one ofinformation for identifying a location the substrate in a lot andinformation for identifying a lot location.

It is also preferred that the identification mark is described by thesame material as that of the terminal cover layers (bump cover layers)and/or a seed layer thereof deposited on the input and output terminals(bumps). In a process for forming the bump cover layers of the bumps, atfirst, the seed layer for the bump cover layers is deposited on theprotection layer. The identification mark can be made by applying thelaser beam to the seed layer or to the bump cover layers itself so as tomachine it to remain irradiation traces of the material of the seedlayer or to the bump cover layers on the protection layer.

Preferably, the identification mark is formed in a region outside of theinput and output terminals. Since input and output wires will beconnected to the terminals, it is desired the mark is formed in theoutside region of these terminals.

It is preferred that the identification mark is represented by spots ofa binary code such as a BCD code. If the binary code is used instead ofcharacters and numerals, larger amount of the information can be writtenin a smaller area. Using of the binary code is also effective for makingvery easy the laser beam machining process of the identification markbecause it can be represented by spots.

According to the present invention, also a method of manufacturing thinfilm magnetic heads including a step of forming, on one surface of asubstrate, a plurality of electromagnetic transducer elements and aplurality of input and output terminals electrically connected to thetransducer elements, a step of forming a protection layer on the surfaceof the substrate to cover at least the transducer elements, and a stepof forming identification marks for identifying the respective magnetichead, on the protection layer on the surface of the substrate by meansof laser beam machining is provided.

Since the identification mark is formed on the protection layer, thisidentification mark can be made in any region outside of the bumps.Namely, the identification mark can be made even on the transducerelements and on the lead conductors. Thus, enough amount ofidentification information can be written even if the thin film magnetichead is greatly downsized. Furthermore, since the identification marksare formed on the element-forming face of the substrate, theseidentification marks can be held even if a portion of the wafer near itsrear surface is sliced and removed due to downsizing. Therefore,management of each of magnetic heads is possible in any manufacturingprocesses after the aforementioned bump cover forming process. Laserbeam machining of the identification marks can result usage of nophotomask and easy formation of arbitrary marks. Also, as preciselocation of the identification marks will not be required, a low costlaser can be used.

It is very preferred that the identification mark forming step includesa step of forming identifying information which can differ for eachsubstrate by means of laser beam machining.

In order to make the identification mark by photolithograph as in theconventional art, it is necessary to use a photomask. Although the samephotomask can be commonly used for making an identification markrepresenting a slider identifying information such as a locationinformation of the slider in a substrate, different photomasks forrespective substrates or lots should be used for making anidentification mark representing substrate identifying information suchas a location information of the substrate in a lot or a lot number.Thus, a great number of the photomasks has to be prepared. However, thelaser beam machining of the identification marks can result usage of nophotomask and easy formation of arbitrary marks such as anidentification mark representing substrate identifying information suchas a location information of the substrate in a lot or a lot numberwithout increasing a number of the photomask.

It is also preferred that the method further includes a terminal coverforming step of forming terminal cover layers and a seed layer thereofon the surface in order to cover the input and output terminals,respectively, and that the identification mark forming step is performedduring this terminal cover layer forming step.

Since the seed layer of such as titanium and gold acts as a layer forlaser beam reflection and absorption, for laser beam scattering and forheat absorption, the transducer elements and lead conductors formedbelow this seed layer are protected from destructions caused by metalfusion or boundary face stripping due to the laser beam striking throughthe protection layer which is in general formed by a material easilytransmitting the laser beam. To form the identification mark on theprotection layer results no modification of process conditions in aconventional process. Therefore, the formation process of theidentification mark can be very easily introduced into the manufacturingprocesses of the magnetic head.

Preferably, the identification mark forming step includes a step offorming the identification marks in regions outside of the input andoutput terminals. Since input and output wires will be connected to theterminals, it is desired the mark is formed in the outside region ofthese terminals.

It is preferred that the terminal cover layer forming step includes astep of forming a seed layer on the protection layer, and a step ofplating gold on the seed layer to make the terminal cover layers, andthat the identification mark forming step includes a step of formingidentification marks on the seed layer by means of laser beam machining.

In this case, the identification mark forming step may include a step ofapplying laser beam to the seed layer through a deposited photoresistlayer. If the laser beam machining is performed after depositing thephotoresist layer for the gold plating, dross which is certainlyproduced by the laser beam machining will be absorbed by thisphotoresist layer to suppress its scattering. Also, since the produceddross can be removed together with the photoresist layer, theelectromagnetic transducer elements will be effectively prevented fromcontamination. Furthermore, the photoresist layer contributes toabsorption of heat produced by the laser beam.

The identification mark forming step may be carried out after or beforethe gold plating step. If it is carried out after the gold plating step,the dross due to the laser beam machining will produce no effect on thisgold plating of the bump cover layers.

The method may further include a step of removing the photoresist layer,and the identification mark forming step may be carried out after orbefore the photoresist layer removing step.

It is preferred that the terminal cover layer forming step includes astep of forming a gold cover layer on the protection layer bysputtering, and a step of making a predetermined patterns of the goldcover layer, and that the identification mark forming step includes astep of forming identification marks on the patterned gold cover layerby means of laser beam machining.

Further objects and advantages of the present invention will be apparentfrom the following description of the preferred embodiments of theinvention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, already described, shows the conventional art for formingidentification number or symbol on a thin film magnetic head;

FIG. 2, already described, shows the conventional art for formingidentification number or symbol on a thin film magnetic head;

FIG. 3 is a plane view schematically showing an air-flow outlet sideface of a preferred embodiment of a thin film magnetic head according tothe present invention;

FIG. 4 is a flow chart of a bump cover forming process of a method ofmanufacturing a thin film magnetic head according to the presentinvention;

FIGS. 5a to 5e are wafer sectional views illustrating the process ofFIG. 4;

FIG. 6 is a schematic view showing an example of a laser beam machineused for a laser beam machining process;

FIGS. 7a and 7b are sectional views respectively showing a process ofthe laser beam machining and a shape of a finally obtainedidentification mark;

FIGS. 8a and 8b are sectional views respectively showing a process ofthe laser beam machining and a shape of a finally obtainedidentification mark;

FIGS. 9a and 9b are sectional views respectively showing a process ofthe laser beam machining and a shape of a finally obtainedidentification mark;

FIGS. 10a and 10b are sectional views respectively showing a process ofthe laser beam machining and a shape of a finally obtainedidentification mark;

FIGS. 11a and 11b are sectional views respectively showing a process ofthe laser beam machining and a shape of a finally obtainedidentification mark;

FIGS. 12a to 12e are wafer sectional views illustrating a modified bumpcover forming process based upon the process shown in FIG. 4;

FIG. 13 is a flow chart of an another bump cover forming process of amethod of manufacturing a thin film magnetic head according to thepresent invention;

FIGS. 14a to 14e are wafer sectional views illustrating the process ofFIG. 13;

FIG. 15 is a flow chart of a further bump cover forming process of amethod of manufacturing a thin film magnetic head according to thepresent invention;

FIGS. 16a to 16e are wafer sectional views illustrating the process ofFIG. 15;

FIG. 17 is a flow chart of a still further bump cover forming process ofa method of manufacturing a thin film magnetic head according to thepresent invention;

FIGS. 18a to 18e are wafer sectional views illustrating the process ofFIG. 17;

FIG. 19 is a flow chart of an another bump cover forming process of amethod of manufacturing a thin film magnetic head according to thepresent invention; and

FIGS. 20a to 20e are wafer sectional views illustrating the process ofFIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 3 which schematically shows an air-flow outlet side face of apreferred embodiment of a thin film magnetic head according to thepresent invention, reference numeral 30 denotes a slider and 30a denotesan air-flow outlet side face of the slider 30. On this end face 30a, anelectromagnetic transducer element or a read/write magnetic head element31, its input and output terminals (bumps) 32 and lead conductors 33electrically connecting the transducer element 31 with the bumps 32 areformed by using a photolithography technology, a thin film formingtechnology and an etching technology for example.

In a portion on the end face 30a, which is not occupied by thetransducer element 31, the bumps 32 and the lead conductors 33, a firstidentification mark 34 represented by numerals, characters or binarycodes is formed. This first identification mark 34 is a slideridentifying information which indicates a location of the slider 30 inthe substrate (wafer) such as for example a bar number and/or a piecenumber of this slider. The same mark 34 will be written for the slidersat the same location in different wafers. This mark 34 can be formed byphotolithography using a common photomask for different wafers.

As is not clearly illustrated in FIG. 3, whole area of the end face 30aof the completed head except for regions of the bumps 32 is covered by aprotection layer. On the protection layer, a second identification mark35 is formed as irradiation traces by means of laser beam. This mark 35is a wafer identifying information which indicates for example alocation of the wafer in a lot and/or a lot number and which can bediffer for each wafer. This mark 35 may be not the same for differentwafers.

This second identification mark 35 is made of a material formingterminal cover layers for covering the respective bumps 32 (bump coverlayers) or a material of a seed layer of the bump cover layers. In aprocess for forming the bump cover layers of the bumps 32, at first, theseed layer for the bump cover layers, made of materials of for examplegold and titanium is deposited. As will be described later in detail,the second identification mark 35 is made by applying the laser beam tothe seed layer or to the bump cover layers itself so as to machine it toremain irradiation traces of gold and titanium on the protection layer.

Since the second identification mark 35 is formed on the protectionlayer, this identification mark 35 can be made in any region on the endface 30a so long as presence of the protection layer. Namely, the secondidentification mark 35 can be made even on the transducer element 31 andthe lead conductors 33. Thus, enough amount of identificationinformation can be written on the end face 30a even if the thin filmmagnetic head is greatly downsized. It is desired that the secondidentification mark is formed outside of the bumps 32 because input andoutput wires will be connected thereto. However, if there are remainedareas in the bumps 32 after the connection of the input and outputwires, the second identification mark may be written on the remainedareas within the bumps 32. To form the second identification mark 35 onthe protection layer will result no modification of process conditionsin a protection layer deposition process which may be one of the mostdifficult manufacturing processes of the thin film magnetic head.Therefore, the formation process of the second identification mark canbe very easily introduced into the manufacturing processes of themagnetic head.

Furthermore, since the identification marks 34 and 35 are formed on theelement-forming face 30a of the slider 30 (on the front surface of thesubstrate), these identification marks can be held even if a portion ofthe substrate near its rear surface is sliced and removed due todownsizing.

The second identification mark 35 is, in this embodiment, represented byBCD (Binary-Coded Decimal) code. However, this second identificationmark 35 can be represented either by a binary code other than the BCDcode or by characters and/or numerals. If the binary code is usedinstead of characters and numerals, larger amount of the information canbe written in a smaller area. Using of the binary code is also effectivefor making very easy the laser beam machining process of the secondidentification mark 35 because it can be represented by spots. In orderto represent the second identification mark 35 by the binary code ofspots arranged in a matrix (for example five lines and five columns), itmay be necessary to know which is the top side or bottom side of thematrix. For this purpose, it may be determined that spots atpredetermined positions in the matrix (for example spots at fourth lineand second column, at fifth line and second column, at fifth line andthird column, and at fifth line and fourth column) are always existed sothat these spots are used as a symbol for indicating the top side orbottom side of the matrix.

In the aforementioned embodiment, only the second identification markwhich indicates wafer identifying information is formed by the laserbeam machining. However, a first identification mark indicating alocation of the wafer or another information indicating for examplespecification of the head can be formed by the laser beam machining.

FIG. 4 shows a bump cover forming process of a method of manufacturing athin film magnetic head according to the present invention, and FIGS. 5ato 5e sectionally show the process of FIG. 4. Hereinafter, referring tothese figures, the bump cover forming process will be described indetail.

On a front surface (element-forming face) of a wafer, a plurality ofelectromagnetic transducers, a plurality of bumps made of for examplecopper, and a plurality of lead conductors electrically connecting thetransducers with the respective bumps, such as shown in FIG. 3 areformed and after that a protection layer is formed thereon, inaccordance with the known processes.

In the bump cover forming process carried out after these processes, atfirst, the protection layer 50 is ground and polished to bare a surfaceof the bumps 51 (step S40).

Then, as a seed layer for gold (or platinum) plating which constitutesthe bump cover, a titanium layer 52 and a gold layer 53 are sequentiallydeposited on the ground protection layer 50 and on the bared bumps 51 bysputtering for example (step S41). Thicknesses of the deposited titaniumlayer 52 and the deposited gold layer 58 are for example 50 Angstromsand 500 Angstroms, respectively. The titanium layer 52 serves as anadhesive layer which may be made by chrome or tantalum other thantitanium.

On the seed layer 53, a negative type photoresist layer 54 is coated(step S42). This coated photoresist layer 54 is then exposed to forexample ultraviolet radiation with a mask having a predetermined bumpcover pattern (step S43) and developed (step S44) so as to obtain alayer structure as shown in FIG. 5a.

Then, laser beams 55 are radiated to the photoresist layer 54 which isformed on the seed layer except for the regions of the bumps 51, tomachine a part of the photoresist layer 54 and the seed layer 52, 53 sothat an identification mark such as the second identification mark 35shown in FIG. 3, which indicates wafer identifying information (forexample a location information of the wafer in a lot or a lot number),by a binary code such as a BCD code (step S45). Namely, as shown in FIG.5b, each laser beam 55 makes a hole 54a in the photoresist layer 54 andchanges properties of the seed layer 52, 53 of a circular portion underthe hole 54a. In case that YAG laser beam with a spot diameter of 10 μmis radiated to the negative type photoresist layer 54, the hole 54a withan internal diameter of 0-8 μm is made in the photoresist layer 54 andalso the properties of titanium and gold of the seed layer 52, 53 withinthe circular portion with a diameter of 16 μm is changed.

FIG. 6 shows an example of a laser beam machine used for this laser beammachining process. In the figure, reference numeral 60 denotes a YAGlaser beam with a diameter of 1.2 mm, 61 denotes a beam expander, 62denotes a programmable data mask, 63 denotes a reduction lens, and 64denotes a wafer which is positioning controlled along longitudinal andlateral axes, respectively. Another general type laser beam machinessuch as a scanning type laser beam machine using a galvanomirror or apolygon mirror may be used for this laser beam machining process otherthan the mask reduced projection type laser beam machine shown in FIG.6.

After the laser beam machining process, the wafer is subjected to aslight ashing process (step S46). As a result, the surface of the seedlayer 53 at the regions of the bumps 51 is purified, the diameter of theholes 54a is increased by 1-2 μm, and also the properties-changedportions around the holes 54a are eliminated. Thereafter, gold platingis performed (step S47). Thus, terminal cover layers (bump cover layers)made of gold 56 are formed as shown in FIG. 5c. If the photoresist layer34 is made of a positive type photoresist material, a hard bakingprocess will be performed instead of the ashing process.

Then, as shown in FIG. 5d, the photoresist layer 54 is removed (stepS48). After that, the seed layer of titanium and gold 52 and 53 exceptfor that under the bump cover layers 56 is removed by milling operation(step S49). Thus, as shown in FIG. 5e, a part of the properties-changedportions caused by the laser beam machining will finally remain as anidentification mark

Then the wafer is cut in a plurality of rectangular sliced blocks (bars)so that each of the bars includes a plurality of the thin film magnetichead elements aligned in a single-row. Thereafter, one surface of eachof the sliced bars is subjected to a grinding process to shape contoursuch as two rails, and the air bearing surfaces (ABSs) of the rails aresubjected to a lapping process to obtain a desired throat height. Then,by performing the similar processes as the conventional manufacturingprocesses, a separated individual magnetic head can be finally obtained.

FIGS. 7a, 8a, 9a, 10a and 11a show processes of the laser beammachining, and FIGS. 7b, 8b, 9b, 10b and 11b show shapes of finallyobtained identification marks, for various laser beam conditions andvarious photoresist materials, respectively. FIGS. 7a and 7b are a casewherein an ultraviolet laser beam from a gas laser such as a He--Cdlaser or an excimer laser is radiated, FIGS. 8a and 8b are a casewherein a relatively low power laser beam from a YAG laser is radiatedto a negative type photoresist layer, FIGS. 9a and 9b are a case whereina medium power laser beam from a YAG laser is radiated to a negativetype photoresist layer, FIGS. 10a and 10b are a case wherein arelatively high power laser beam from a YAG laser is radiated to anegative type photoresist layer, and FIGS. 11a and 11b are a casewherein a laser beam from a YAG laser is radiated to a positive typephotoresist layer.

As will be understood from these figures, variously shapedidentification marks 57 are finally formed depending upon shapes of theholes 54a opened in the photoresist layer 54 by means of the laser beammachining. The identification mark 57 in the case shown in FIG. 7b issubstantially constituted by a cylindrical shaped gold plate, the marks57 in both cases shown in FIGS. 8b and 9b are constituted byproperties-changed seed layers with ring shape, and the marks 57 in bothcases shown in FIGS. 10b and 11b are constituted by properties-changedseed layers with ring shapes and also by ring-shaped gold plate. All ofthe identification marks 57 shown in FIGS. 7a and 7b to 11a and 11b canbe easily and externally identified. It should be noted that, for thelaser beam machining, a solid laser such as the YAG laser can be treatedeasier than the ultraviolet gas laser which is relatively expensive anddifficult for maintenance.

According to the aforementioned process, since the laser beam machiningis performed after coating the photoresist layer 54 for the goldplating, dross which is certainly produced by the laser beam machiningwill be absorbed by this photoresist layer 54 to suppress itsscattering. Also, since the produced dross can be removed together withthe photoresist layer 54, the electromagnetic transducer elements willbe effectively prevented from contamination. Furthermore, thephotoresist layer 54 contributes to absorption of heat produced by thelaser beam. In addition, since the seed layer of titanium and gold 52and 53 acts as a layer for laser beam reflection and absorption, forlaser beam scattering and for heat absorption, the transducer elementsand lead conductors formed below this seed layer are protected fromdestructions caused by metal fusion or boundary face stripping due tothe laser beam striking through the protection layer 50 which is ingeneral formed by a material easily transmitting the laser beam.

According to this process, the identification mark 57 can be made in anyregion outside of the bumps 51. Namely, the identification mark 57 canbe made even on the transducer elements and on the lead conductors.Thus, enough amount of identification information can be written even ifthe thin film magnetic head is greatly downsized. Although it is desiredthat the identification mark is formed outside of the bumps 51 becauseinput and output wires will be connected thereto, if there are remainedareas in the bumps 51 after the connection of the input and outputwires, the identification mark may be formed on the remained areaswithin the bumps 51.

Furthermore, according to the process, since the identification marksare formed on the element-forming face (front surface) of the wafer,these identification marks can be held even if a portion of the wafernear its rear surface is sliced and removed due to downsizing.Therefore, management of each of magnetic heads is possible in anymanufacturing processes after the aforementioned bump cover formingprocess.

Laser beam machining of the identification marks can result usage of nophotomask and easy formation of arbitrary marks. For example, a secondidentification mark representing wafer identifying information such as alocation information of the wafer in a lot or a lot number can be easilyformed without increasing a number of the photomask. Also, as preciselocation of the identification marks will not be required, a low costlaser can be used.

To form the identification mark on the protection layer 50 results nomodification of process conditions in a protection layer depositionprocess which may be one of the most difficult manufacturing processesof the thin film magnetic head. Therefore, the formation process of theidentification mark can be very easily introduced into the manufacturingprocesses of the magnetic head.

The identification mark can be represented either by a binary code otherthan the BCD code or by characters and numerals. If the binary code isused instead of characters and/or numerals, larger amount of theinformation can be written in a smaller area. Using of the binary codeis also effective for making very easy the laser beam machining processof the identification mark because it can be represented by spots.

In the aforementioned process, the identification mark which indicateswafer identifying information is formed by the laser beam machining.However, another identification mark indicating a location of the waferor indicating for example specification of the head can be formed by thelaser beam machining.

FIGS. 12a to 12e illustrate a modified bump cover forming process basedupon the process shown in FIG. 4. In these figures, reference numeral120 denotes a protection layer, 121 denotes bumps, 122 and 123 denote atitanium layer and a gold layer which constitute a seed layer for goldplating, 124 denotes a negative type photoresist layer, 124a denoteholes formed by a laser beam machining in the photoresist layer 124, 125denote laser beams, 126 denotes bump cover layers of gold, and 127denotes a finally formed identification mark.

In this modified process, a protection cover 128 shown in FIG. 12d isformed to cover a region of the identification mark 127 after a step ofremoving the photoresist layer 124 which is the same as the step S48 inthe process of FIG. 4. This protection cover 128 serves to protect theidentification mark 127 from damage due to milling operation which willbe performed for removing the seed layer of titanium and gold 122 and123 except for that under the bump cover layers 126 as shown in FIG.12e. Operations in another steps in this modified bump cover formingprocess and advantages therefrom are the same as those in the process ofFIG. 4.

FIG. 13 shows an another bump cover forming process of a method ofmanufacturing a thin film magnetic head according to the presentinvention, and FIGS. 14a to 14e sectionally show the process of FIG. 13.In this process, a laser beam machining step is carried out Just after agold plating step. Hereinafter, referring to these figures, the bumpcover forming process will be described in detail.

In FIGS. 14a to 14e, reference numeral 140 denotes a protection layer,141 denotes bumps, 142 and 143 denote a titanium layer and a gold layerwhich constitute a seed layer for gold plating, 144 denotes a negativetype photoresist layer, 144a denote holes formed by a laser beammachining in the photoresist layer 144, 145 denote laser beams, 146denotes bump cover layers of gold, and 147 denotes a finally formedidentification mark.

Operations in steps S130 to S134 in FIG. 13 are the same as those in thesteps S40 to S44 in FIG. 4, respectively. After the developing step S134which provides a layer structure as shown in FIG. 14a, the wafer issubjected to a slight ashing process (step S135). As a result, thesurface of the seed layer 143 at the regions of the bumps 141 ispurified, and then gold plating is performed (step S136). Thus, terminalcover layers (bump cover layers) 146 made of gold are formed as shown inFIG. 14b.

Then, the laser beams 145 are radiated to the photoresist layer 144which is formed on the seed layer except for the regions of the bumps141, to machine a part of the photoresist layer 144 and the seed layer142, 143 so that an identification mark such as the secondidentification mark 35 shown in FIG. 3, which indicates waferidentifying information (for example a location information of the waferin a lot or a lot number), by a binary code such as a BCD code (stepS137). Namely, as shown in FIG. 14c, each laser beam 145 makes the hole144a in the photoresist layer 144 and changes properties of the seedlayer 142, 143 of a circular portion under the hole 144a.

Operations in steps S138 and S139 in FIG. 13 are also the same as thosein the steps S48 and S49 in FIG. 4, respectively.

According to the above-mentioned process, since the laser beam machiningis performed after the gold plating of the bump cover layers 146 on thebumps 141, dross which is certainly produced by the laser beam machiningwill produce no effect on this gold plating of the bump covers 146.According to this process, because no plated gold layer is formed in theholes 144a in the photoresist layer 144, the finally obtainedidentification mark 147 has a shape as shown in FIG. 14e, which is thesame as that shown in FIGS. 8b and 9b. Operations in another steps inthis modified bump cover forming process and advantages therefrom arethe same as those in the process of FIG. 4.

FIG. 15 shows a further bump cover forming process of a method ofmanufacturing a thin film magnetic head according to the presentinvention, and FIGS. 16a to 16e sectionally show the process of FIG. 15.In this process, a laser beam machining step is carried out after aphotoresist layer removing step. Hereinafter, referring to thesefigures, the bump cover forming process will be described in detail.

In FIGS. 16a to 16e, reference numeral 160 denotes a protection layer,161 denotes bumps, 162 and 163 denote a titanium layer and a gold layerwhich constitute a seed layer for gold plating, 164 denotes a negativetype photoresist layer, 165 denote laser beams, 166 denotes bump coverlayers of gold, and 167 denotes a finally formed identification mark.

Operations in steps S150 to S154 in FIG. 15 are the same as those in thesteps S40 to S44 in FIG. 4, respectively. After the developing step S154which provides a layer structure as shown in FIG. 16a, the wafer issubjected to a slight ashing process (step S155). As a result, thesurface of the seed layer 163 at the regions of the bumps 141 ispurified, and then gold plating is performed (step S156). Thus, terminalcover layers (bump cover layers) 166 made of gold are formed as shown inFIG. 16b.

Then, as shown in FIG. 16c, the photoresist layer 164 is removed (stepS157). After that, the laser beams 165 are radiated to the seed layerexcept for the regions of the bump cover layers 166, to machine a partof the seed layer 162, 163 so that an identification mark such as thesecond identification mark 35 shown in FIG. 3, which indicates waferidentifying information (for example a location information of the waferin a lot or a lot number), by a binary code such as a BCD code (stepS158). Namely, as shown in FIG. 16d, each laser beam 165 changesproperties of the seed layer 162, 163 of a circular portion.

Then, the seed layer of titanium and gold 162 and 163 except for thatunder the bump cover layers 166 is removed by milling operation (stepS159). This milling operation will result to decrease height of theidentification mark 167 and to remove scattered dross with low adhesiondue to the laser beam machining. Thus, as shown in FIG. 16e, a part ofthe properties-changed portions caused by the laser beam machining andsome dross produced by the laser beam machining will finally remain asthe identification mark 167.

According to the above-mentioned process, since the laser beam machiningis performed after the gold plating of the bump cover layers 166 on thebumps 161, the dross due to the laser beam machining will produce noeffect on this gold plating of the bump covers 166. According to thisprocess, because the laser beam is directly radiated to the seed layerand also no gold plating will be carried out after that, the finallyobtained identification mark 167 has a shape as shown in FIG. 16e, whichis the same as that shown in FIGS. 8b and 9b. However, since the laserbeam machining is carried out after the photoresist layer 164 isremoved, this process cannot expect the photoresist material to absorbthe dross produced by the laser beam machining and heat produced by thelaser beam. Operations in another steps in this modified bump coverforming process and advantages therefrom are the same as those in theprocess of FIG. 4.

FIG. 17 shows a still further bump cover forming process of a method ofmanufacturing a thin film magnetic head according to the presentinvention, and FIGS. 18a to 18e sectionally show the process of FIG. 17.In this process, a laser beam machining step is carried out before aphotoresist layer coating step. Hereinafter, referring to these figures,the bump cover forming process will be described in detail.

In FIGS. 18a to 18e, reference numeral 180 denotes a protection layer,181 denotes bumps, 182 and 183 denote a titanium layer and a gold layerwhich constitute a seed layer for gold plating, 184 denotes a negativetype photoresist layer, 185 denote laser beams, 186 denotes bump coverlayers of gold, and 187 denotes a finally formed identification mark.

Operations in steps S170 and S171 in FIG. 17 are the same as those inthe steps S40 and S41 in FIG. 4, respectively. After the sputtering stepS171 which forms the seed layer of the titanium layer 182 and the goldlayer 183, the wafer is subjected to a laser beam machining process(step S172). At this step S172, the laser beams 185 are radiated to theseed layer except for the regions of the bumps 181, to machine a part ofthe seed layer 182, 183 so that an identification mark such as thesecond identification mark 35 shown in FIG. 3, which indicates waferidentifying information (for example a location information of the waferin a lot or a lot number), by a binary code such as a BCD code. Namely,as shown in FIG. 18a, each laser beam 185 changes properties of the seedlayer 182, 183 of a circular portion.

Operations in steps S173 to S179 in FIG. 17 are also the same as thosein the steps S42 to S49 other than the laser beam machining step S45 inFIG. 4, respectively.

The seed layer of titanium and gold 182 and 183 except for that underthe bump cover layers 186 is removed by the milling operation at thestep S179 resulting to decrease height of the identification mark 187and to remove scattered dross with low adhesion due to the laser beammachining. Thus, as shown in FIG. 18e, a part of the properties-changedportions caused by the laser beam machining and some dross produced bythe laser beam machining will finally remain as the identification mark187.

According to this process, because the laser beam is directly radiatedto the seed layer and also the gold plating is carried out after that,the finally obtained identification mark 187 has a shape as shown inFIG. 18e, which is the same as that shown in FIGS. 8b and 9b. However,since the laser beam machining is carried out before the photoresistlayer 184 is formed, this process cannot expect the photoresist materialto absorb the dross produced by the laser beam machining and heatproduced by the laser beam. Operations in another steps in this modifiedbump cover forming process and advantages therefrom are the same asthose in the process of FIG. 4.

FIG. 19 shows an another bump cover forming process of a method ofmanufacturing a thin film magnetic head according to the presentinvention, and FIGS. 20a to 20e sectionally show the process of FIG. 19.In this process, bump cover layers are formed by sputtering instead ofplating. Hereinafter, referring to these figures, the bump cover formingprocess will be described in detail.

On a front surface (element-forming face) of a wafer, a plurality ofelectromagnetic transducers, a plurality of bumps made of for examplecopper, and a plurality of lead conductors electrically connecting thetransducers with the respective bumps, such as shown in FIG. 3 areformed and after that a protection layer is formed thereon, inaccordance with the known processes.

In the bump cover forming process carried out after these processes, atfirst, the protection layer 200 is ground and polished to bare a surfaceof the bumps 201 (step S190).

Then, a titanium layer 201 and a gold layer 203 which constitute a bumpcover layer are sequentially deposited on the ground protection layer200 and on the bared bumps 201 by sputtering (step S191). Thicknesses ofthe deposited titanium layer 202 and the deposited gold layer 203 arefor example 50 Angstroms and 1 μm, respectively. The titanium layer 202serves as an adhesive layer which may be made by chrome or tantalumother than titanium.

On the bump cover layer 203, a negative type photoresist layer 204 iscoated (step S192). This coated photoresist layer 204 is then exposed tofor example ultraviolet radiation with a mask having a predeterminedbump cover pattern and a predetermined mark forming region pattern (stepS193) and developed (step S194) so as to obtain a layer structure asshown in FIG. 20b.

Then, laser beams 205 are radiated to the photoresist layer 204 which isformed on the bump cover layer except for the regions of the bumps 201and for the mark forming region, to machine a part of the photoresistlayer 204 so that an identification mark such as the secondidentification mark 35 shown in FIG. 3, which indicates waferidentifying information (for example a location information of the waferin a lot or a lot number), by a binary code such as a BCD code (stepS195). Namely, as shown in FIG. 20c, the laser beam 205 draws a negativepattern of the identification mark on the photoresist layer 204 so thatonly portions of the photoresist layer 204 corresponding to the mark areremained. During this machining, the bump cover layer (203 and 202) witha thickness near the laser wave length will act as a reflection layer ofthe laser beam.

After the laser beam machining process, the wafer is subjected to amilling process (step S196). Thus, the bump cover layer (202 and 203) inregions with no photoresist layer 204 is eliminated. As a result, thebump cover layers of gold are formed at the regions of the bumps 201 andthe identification mark made of the gold bump cover layer is formed asshown in FIG. 20d. Then, all the remained photoresist layer 204 isremoved (step S197) and thus the gold bump cover layers (202 and 203)and the identification mark 207 are finally obtained as shown in FIG.20e.

According to the aforementioned process, since the laser beam machiningis performed after forming the bump cover layer, dross which iscertainly produced by the laser beam machining will be absorbed by thisbump cover layer to suppress its scattering. Also, the bump cover layercontributes to absorption of heat produced by the laser beam. Namely,since the bump cover layer acts as a layer for laser beam reflection andabsorption, for laser beam scattering and for heat absorption, thetransducer elements and lead conductors formed below this cover layerare protected from destructions caused by metal fusion or boundary facestripping due to the laser beam striking through the protection layer200 which is in general formed by a material easily transmitting thelaser beam. The finally obtained identification mark 207 has a shape asshown in FIG. 20e, which is the same as that shown in FIG. 7b.Operations in another steps in this modified bump cover forming processand advantages therefrom are the same as those in the process of FIG. 4.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. A thin film magnetic head, comprising:a sliderwith at least one end face; at least one electromagnetic transducerelement formed on said end face of said slider; a plurality of input andoutput terminals formed on said end face of said slider and electricallyconnected to said transducer element; a protection layer formed on saidend face to cover at least said transducer element; terminal coverlayers and a seed layer thereof, formed on said end face to cover saidinput and output terminals; and an identification mark for identifyingsaid magnetic head, described on said protection layer on said end faceof the slider, wherein said identification mark is described by the samematerial as that of said terminal cover layers or said seed layer. 2.The thin film magnetic head as claimed in claim 1, wherein said magnetichead is one of a plurality of thin film magnetic heads produced from asingle substrate, and wherein said identification mark represents anidentifying information which can differ for each substrate.
 3. The thinfilm magnetic head as claimed in claim 2, wherein said identifyinginformation includes at least one of information for identifying alocation the substrate in a lot and information for identifying a lotlocation.
 4. The thin film magnetic head as claimed in claim 1, whereinsaid identification mark is formed in a region outside of said input andoutput terminals.
 5. The thin film magnetic head as claimed in claim 1,wherein said identification mark is represented by spots of a binarycode.